5 questions on meteors/asteroids, answered

A piece of a meteorite, about the size of a walnut, whose impact broke windows and rattled shelves in St. Mary's County in 1919.

A piece of a meteorite, about the size of a walnut, whose impact broke windows and rattled shelves in St. Mary's County in 1919. (Baltimore Sun archive)

Scott Dance, The Baltimore Sun

As if some weren't already on edge with the prospect of an asteroid passing 17,000 miles from Earth, a meteorite exploded over Russian skies injuring 500 people. Scientists say the two aren't related, but there is a long list of questions many may have beyond that.

Here are some answers, according to Richard Henry, academy professor in Johns Hopkins University's Henry A. Rowland Department of Physics and Astronomy:

What is the difference between a meteor and an asteroid?

A meteor is a (usually tiny, tiny, thank goodness) asteroid that happens to hit Earth.

17,000 miles doesn’t sound like much. How are scientists sure the asteroid is going to miss Earth?

We're just damned good. Sorry for being facetious, but it is true. The motion is very predictable, thanks to Isaac Newton.

How did the meteorite over Russia go undetected?

Easily, most meteors (the overwhelming majority) go undetected. Thousands of them impact Earth every day, but only rarely one this big of course.

How do scientists track asteroids and predict close passes that are years or decades away?

By photographing large parts of the sky every day, day after day, and computing orbits for detected asteroids.

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And a bonus sixth question answered: How often do meteorites strike Maryland?

Not often, but it has happened. In 2011, a man who said he witnessed a falling meteor in Frederick told the Frederick News-Post that he found pieces of it later. In 2002, NASA confirmed that a Pasadena man recovered a meteorite that fell in the woods behind his home, according to Sun archives.

Before that, Smithsonian records show four previous meteorite finds in Maryland. The earliest was a 16 1/2-pound rock found in Charles County; a 1 pound iron meteorite was found near Emmitsburg in 1854; a 3-pounder was discovered in Garrett County in 1888; and another fell near St. Jerome's Creek in St. Mary's County in 1919.